Since its inception in FY2012, the mass spectrometry facility within CPTR collaborated in 15 different projects and analyzed more than 650 samples. Those projects address a variety of biological questions addressed primarily by one of two applications of protein mass spectrometry. One of the most common uses is to identify the entire proteome of a specific sample, such as an organelle, or to identify enriched protein interactors. We have collaborated of seven projects of this type, among them: characterization of the proteome of organelles purified from vegetative and developing Dictyostelium; identification of protein interactors of Arf-GAP proteins; identification of interactors of the delta133 isoform of p53; relative quantitation of secreted proteomes; and protein targets of a small molecule inhibitor. Mass spectrometry analysis is also a leading method to identify sites of post-translational modification on proteins. We have worked on six projects that involve identification protein modifications, including ubiquitination, hosphorylation, methylation, acetylation, and covalent modification by a two different small molecule inhibitors. Currently, many of these projects are still ongoing. Thus far, they have produced very interesting results for the collaborator and suggested specific hypotheses to be tested in follow-up experiments.